This invention relates to a method and an apparatus for hydrolysis treatment of cellulosic fiber material.
In conventional systems, wood chips (or other cellulosic or fiber material) can undergo hydrolysis in a single vessel prior to treatment or cooking in a digester, such as described in U.S. Pat. Nos. 3,380,883 and 3,413,189. In such systems, hydrolysis occurs under acidic conditions in the slurry of wood chips, e.g., cellulosic material, passing through a top section of the vessel with the continued treatment of cooking in lower sections of the vessel followed by washing in the bottom of the vessel. In the upper region of the vessel, hydrolysate, e.g., sugars such pentose and hexose, is extracted from wood chips and the hydrolysate is recovered.
Hydrolysis occurs throughout the upper region of the vessel by the introduction of steam, acid and/or water in a con-current flow in the upper region. In the lower region of the vessel, the cellulosic material is cooked and wash and is subsequently discharged as pulp from the vessel.